Telecommunication System for Automatically Locating by Network Connection and Selectively Delivering Calls to Mobile Client Devices

ABSTRACT

A communication system for an organization having multiple sites uses a dual-mode device capable of both cell phone communication and telephone communication on a local area network (LAN). IP LANS are established at organization sites such that a temporary IP address is assigned to a dual-mode device that logs onto an organization LAN, and the IP address is associated at a PSTN-connected server on the LAN with the cell phone number of the communication device. The IP server notifies a PSTN-connected routing server when a device logs on to a LAN, and also provides a destination number for the IP server. Cell calls directed to the device are then redirected to the IP server and directed to the device connected to the LAN.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present Invention is in the field of telephony communicationsincluding data network telephony (DNT), which encompasses InternetProtocol Network Telephony (IPNT), and pertains more particularly tomethods and apparatus for locating by network connection and selectivelydelivering calls to mobile client devices.

2. Description of Related Art

The art of telephony communication has grown in proportion with improvedtelephony infrastructure, equipment, and methods of practice.Conventionally and historically telephone communication has beenpracticed by use of networks that provide dedicated connections andguaranteed bandwidth, such as in Publicly Switched Telephony Networks(PSTN). In such networks a call placed from a telephone connected to alocal service is switched over dedicated channels to a destination, andas long as the connection is maintained, the dedicated path, having adedicated bandwidth, is also maintained. Such networks may be termedConnection Oriented/Switched Telephony (COST) networks.

More recently, with the development of extensive data networks, of whichthe well-known Internet is a prime example, a newer type of telephonycommunication has been introduced. This form of telephony is termedherein Data Network Telephony (DNT), and, in the context of the Internetdata network Internet Protocol Network Telephony (IPNT). Data networkstypically link computers over one or more sub-nets, which may includelocal area networks (LAN), wide area networks (WAN) such as theInternet, company Intranets, and combinations of these and other datanetworks. IPNT telephony may be practiced on any suitableswitched-packet data network whether wired or wireless provided suitableprotocol is supported.

In DNT, such as IPNT, dedicated connections are not generally provided.Instead, digital audio data is prepared in standardized audio packetscomplete with header information and the like. The packets are preparedin near real-time and broadcast over the data network(s) connectinginvolved computers or telecommunications devices adapted for DNTapplications. The header for each packet includes a destination for thepacket.

Data Network Telephony, such as IPNT is well known in the art, andwireless data transmission is also quite well known in manyapplications. Internet service providers, for example, are recentlyproviding high data-rate wireless Internet access by satellite systems,and, where bandwidth is not substantially restricted at the receiver'send.

The problems for Data Network Telephony in wireless systems are relatedto the real-time nature of telephony data and the typically limitedbandwidth available in such systems. In relatively high-bandwidthsystems having a relatively large number of users the distributionprobabilities provide a situation where it is uncommon for several ormany users to demand unusual bandwidth at the same time. The phenomenonis known in the art as averaging. Even with known high-use times, it canbe expected that distribution will be such that bandwidth will beadequate.

A contributing problem is in the nature of real-time audio data asopposed to data transmitting stored documents and the like, which may becalled data-data as opposed to voice-data. Data-data such as graphicsfiles, text files, and the like are stored and prepared for transmissionwherein the file size is known. Late-arriving packets is not an issue asdownloading is not complete until every packet is received. If for somereason transmission is lost, a re-connect may be performed to retrievethe rest of the file. Voice-data packets for real-time conversations aredifferent. The packets for voice-data have to be prepared andtransmitted in essentially real time in both directions or a meaningfulconversation cannot be held. COST connections and wireless connections,wherein bandwidth is assured, have no problem with real-time voicecommunication.

More recent developments regarding quality-of-service (QOS) andanalog-to-IPNT conversion and compression techniques have greatlyimproved the capability of IP networks having a lesser assurance ofavailable bandwidth to facilitate real-time communication wherein thecaller is calling from a cellular or a COST network.

With respect to Internet Protocol (IP) networks that are private and setup by companies to, for example, cover a large technical campus, it isknown to the inventors that calls may arrive from COST or cellulardigital networks, and to be converted to IPNT format for distribution toaddressed telecommunications devices that are connected to the network.For example, certain connected computers, DNT capable telephones, andthe like are capable of receiving from, and sending calls to a cellularor COST network such as a PSTN network. Such an IP network is usually ofthe form of a wired LAN such as an Extranet or Intranet. However, it isknown to the inventor that such networks may also operate in variouswireless technology modes such as a code-division-multiple-access CDMAor a time-division-multiple-access (TDMA) convention. The well-knowncellular system is typically a variation of the latter. RF, microwave,and infrared technologies are also used. Improvements inbandwidth-reserving technology combined with smart IPNT routingcapability such as is known to the inventor have made accepting COST orcellular calls from an out-side network practical.

Often, company sites maintaining LAN's as described above, whether wiredor wireless, have frequent visitors from other sites, and the visitorsare not resident employees and therefore typically do not haveLAN-connected communication devices personally addressed to them at thevisited campus. Such individuals may be required to move from one siteto another spending an unpredictable time at each site. Consultants,sales people, regional managers, and the like make up this category ofpossible visitors. An especially large organization, such as agovernment organization, may have a large number of such visitors ormobile employees roaming through the sites at any given time.

Typically, such individuals would carry cellular telephones orequivalent devices for communication with, for example, callers from ahome office, or other business calls. Depending on where such anindividual lives or works, he or she may be required to extend themobile communication range of a cellular device. This is termed roamingin the art. If the organization is significantly large or distributedover a large geographic region, he may have to roam over more than oneservice area. The cost of communication on a cellular phone increaseshas he roams further from a primary service area.

Often individuals use telephones designated to resident individuals orworkers at a visited location to avoid costly cell charges. However,such resident individuals may be inconvenienced by having to take callsfor the visitors. If calls are many, the resident individuals duties maybe interrupted. It would be desirable then, to have a cell phone orequivalent device adaptable to a wireless or wired IP network at thelocation or site that a person may be visiting, and have incoming callsforwarded to the connected to the device. Such a telephone device and asystem cooperating with the device, could enable substantial costsavings for the sponsoring organization.

What is clearly needed is a method and apparatus that would allow avisitor to an IP LAN-connected site to plug in or otherwise connect hisor her mobile telephone device to the local IP LAN, so that calls comingfrom any source network may be routed to the user's device on the LAN.

SUMMARY OF THE INVENTION

In a preferred embodiment of the present invention a dual-modecommunication device is provided, comprising microphone and speakerapparatus including converters for rendering audio data as audiblespeech, and for rendering audible speech as audio data; a firstcommunication interface comprising circuitry for receiving and sendingthe audio data on a cell-phone network; and a second communicationinterface comprising circuitry for connecting to a local area network(LAN), and for receiving and sending the audio data on the LAN. In someembodiments the dual-mode communication device is implemented in theform of a cell phone.

In some embodiments the circuitry for connecting comprises a connectorfor engaging a hard-wired LAN. In other embodiments the circuitry forconnecting comprises apparatus for communicating with a wireless IP-LAN.There are control routines for negotiating a temporary IP address withthe LAN upon connecting to the LAN.

In an other aspect of the invention a system for telephone communicationis provided, comprising an IP-LAN including an IP telephony server; adual-mode communication device comprising first apparatus for conductingtelephone calls on a cell-phone network, including a cell-phone number,and second apparatus for conducting telephone calls over the IP-LAN; apublicly-switched telephone network (PSTN) having a trunk connection tothe IP telephony server; and a PSTN-connected routing server. The IPtelephony server, upon connection of the dual-mode communication deviceto the IP-LAN, assigns a temporary IP address to the connected deviceand informs the routing server of the connection and a destinationnumber for the IP telephony server, and wherein the routing server thenroutes calls for the cell phone number to the IP telephony server, whichin turn routes the calls on the IP-LAN to the temporary IP address.

In some embodiments of the system the routing server is hosted by acell-phone network. In other embodiments the routing server is a part ofa PSTN service control point (SCP). The IP-LAN may be a wireless LAN.

In some embodiments the system may have a user-editable profile at thecell-phone routing server, enabling a user to list first originationnumbers for cell network delivery and second origination numbers for LANnetwork delivery, wherein the cell-phone routing server delivers allcalls on the cell network unless the dual-mode communication device islogged onto the LAN, in which case all calls from first originationnumbers are delivered on the cell network and calls from the secondorigination numbers are delivered on the LAN.

In another aspect of the system an IP Local Area Network (IP-LAN) systemis provided, comprising an IP telephony server connected on the LAN andto a publicly-switched telephony trunk; and control routines executingon the IP telephony server. The IP telephony server assigns a temporaryIP address to a cell phone-capable device connecting on the LAN, andcommunicates the fact of connection and a destination number for the IPtelephony server to a PSTN-connected routing server. In this system thePSTN-connected routing server may be hosted by a cell-phone network ormay be a part of a PSTN service control point (SCP). The LAN may be awireless network. In this system the IP telephony server associates thecell number of the cell phone-capable device with the IP address, anddelivers calls received for the cell number to the cell-phone-capabledevice connected on the LAN.

In yet another aspect of the invention a method for minimizing cellphone charges for an organization having multiple sites is provided,comprising steps of (a) providing an IP-LAN at least one organizationsite, the LAN having a PSTN-connected IP server; (b) providing at leastone dual-mode communication device for use by organization personnel,the device capable of connection and communication on both a cell-phonenetwork and on the LAN; (c) assigning a temporary IP address to the oneor more dual-mode communication devices upon connection to the LAN; (d)associating the IP address with the cell phone number of the dual-modecommunication device at the IP server; (e) communicating the cell phonenumber and a destination number for the IP server to a PSTN-connectedrouter; and (f) routing calls for the cell phone number to the dual-modecommunication device via a cell phone network during time the dual-modedevice is not logged on to the LAN, and to the IP server for routing onthe LAN during time the device is logged on to the LAN.

In the method provided, in step (e) the PSTN-connected router may behosted by a cell-network provider or may be a part of a PSTN servicecontrol point (SCP). In embodiments of the invention for the first timea system is provided wherein users may receive cell calls between sitesand may log on to local sites where calls may be delivered by localLANs, thereby minimizing communication costs for the organizationhosting the sites. Embodiments of the invention are disclosed inenabling detail below.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a front view of a cellular phone enhanced with additionalcommunication ports and software according to an embodiment of thepresent invention.

FIG. 2 is an overview of network connection and communication capabilityof the cell phone of FIG. 1.

FIG. 3 is a basic overview of a service-orientated routing and controlsystem used with the cell phone of FIG. 1 according to an embodiment ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to an embodiment of the present invention, a subscriber-basedservice is provided that allows a cellular-capable device to receivecalls routed through a COST network and over a private IP network.

FIG. 1 is a frontal view of a cellular phone 9 enhanced with additionalcommunication ports and software according to an embodiment of thepresent invention. Cellular telephone 9 is capable of communication overa well-known pulse-code modulated/global system for mobile communication(PCM/GSM) cellular network and also capable of communicating on an IPdata network in either a wired or wireless form.

Cellular phone 9 is not, however, the only form of telecommunicationsdevice that may be used to practice the present invention. For example,any type of wireless communication device may be used that may also beadapted for having at least one mode of IP communication via wirelessand or wired connection. The purpose of using a cell phone, such asphone 9 in this embodiment, is because of the existence of readilyavailable and well established global cellular network, and theproliferation of cell-phone users who often frequent company sites orother locations wherein IP networks are established for localcommunication.

Cell phone 9 operates as a normal cellular phone, and through additionalcircuitry and software becomes a multi-purpose device according to anembodiment of the present invention. In one embodiment a communicationport 11 is provided for a user to plug-in to a wired IP network. Port 11may be in one embodiment a standard 10-base T connection. Therefore,cell phone 9 may be plugged into a wired LAN network and become acommunication device on that network.

In a preferred embodiment an adapter port 13 is also provided forcommunication in wireless mode on a wireless IP network having differentprotocols than the currently available cellular/PCS networks (CCNs) ofsuch types as PCM, GSM, CDMA etc. For example, a wireless networkadapter may be plugged in to port 13 to enable such as infrared networkcommunication, microwave communication, or other wireless communicationwherein protocol may not be compatible with CCN protocols.

A client software suite 19 enables a user to select a type of networkfor communication, to select a protocol for voice communication, and toset-up a temporary IP address on a network for the purpose ofidentifying and registering the device for normal operation on thenetwork. Client software 19 may be provided by a plug-in smart card, ormay be pre-loaded into a suitable built-in memory provided and adaptedfor the purpose. A series of selection buttons such as 15 and 17 allow auser to switch modes from cellular to IP communication, and perhaps toswitch from differing types of networks using known protocols that aremade available via client software 19. One such protocol is therecently-developed H323 IP protocol allowing different hardware-baseddevices to communicate with each other over separate networks. There maybe more than 2 selection buttons such as buttons 15 and 17 withoutdeparting from the spirit and scope of the present invention.Alternatively, the program may be given a series of preferences by theuser, and then may negotiate the best possible connection accordingly.It may use such protocols as DHCP etc. to set up IP addresses and soforth. Selection of the network could be according to an order ofpreference, by availability.

In one embodiment of the present invention cell phone 9 is capable oftaking some calls via cellular path while receiving other calls via IPpath. In such a situation, integrating software is provided tocoordinate activity between the two paths. For example, if engaged withan IP call, an incoming cell call would get a busy signal and so on, orit would be redirected to the IP call point, where it would then bepresented as a call-waiting call, if that feature set is available andenabled. In a preferred embodiment, phone 9 may be switched from onenetwork capability to another at the user's discretion.

FIG. 2 is a system overview of a network connection and communicationcapability according to an embodiment of the present invention. A localcellular network 23, a local switch 31 in a PSTN network 25, and aprivate IP network 27 are shown including connection between thenetworks and phone 9.

Cellular network 23 may be any type of CCN such as is known in the art,including but not limited to GSM-X, TDMA, AMPS, D-AMPS, CDMA-X etc. Abase-station-transceiver (BST) 29 is illustrated as a means ofcommunication within network 23. Other related equipment such asadditional base-transceiver-stations (BTS), and base-controller-stations(BCS) are not illustrated within cell network 23, but are assumed to bepresent. It is the number and geographic range of these access stationsthat determine the extent of a given service area.

If a user travels from one designated cellular service area to another,he is said to be roaming. Such a user may elect to have calls forwardedfrom one service area to his current service area. However, there is acharge for this roaming service. The further away a user travels fromhis designated service area, the higher the cost for receiving calls ina visited service area by normal cellular service.

PSTN network 25 may be any type of COST network such as is known in theart. IP network 27 represents a private company network such as may beconstructed to cover a large company site, a series of sites orlocations, or the like.

Within network 23, there is illustrated a mobile-switching-center (MSC)30 that is adapted for storing tables and records of informationassociated with cell network patrons such as cell-phone numbers, avisitor list register (VLR), a home list register (HLR), and so on.Look-up tables such as VLR and HLR tables list who is currentlylogged-in to a particular service area as is well known in the art ofglobal cellular services. Other functions of MSC 30 include interfacingwith wire-line networks such as, in this case, PSTN 25.

MSC 30 is connected via a telephony trunk 33 to the COST telephonyswitch 31 within PSTN network 25. Calls destined to cell phone 9 arriveat PSTN switch 31, and are typically routed to MSC 30, which alsofunctions as a transfer point or switch to local cellular service areacomponents such as BTS 29, and ultimately to a registered user operatingwithin the service boundary as determined by the VLR or HLR conventions.For example, if a user is roaming to a service area other than servicearea 23, then the HLR will list his current service area to which a callmay then be routed through PSTN 25. Similarly, if a cellular callarrives from the designated service area of a user who has roamed to anew service area, the call is forwarded to that area via PSTN 25.

Telephony switch 31 in this embodiment is connected via trunk 37 to anIP switch 35 illustrated within IP network 27. In this case signalconversion from analog to digital form is performed in IP switch 35. Inanother embodiment, a standard gateway such as an SS-7 gateway may beused. IP switch 35 distributes incoming calls over network 27 accordingto existing protocol and infrastructure. For example, if IP network 27comprises a wired network, then a LAN 39 is the medium through whichcalls are delivered. If IP network 27 is a wireless network, then awireless LAN 38 is the medium over which calls are delivered. In somecases, a combination of wired and wireless forms of LAN communication ispossible.

In this exemplary embodiment, cell phone 9 may communicate via cellularnetwork in normal fashion as illustrated via dotted double-arrow 43. Inaddition to normal cellular communication, cell phone 9 may communicatein wireless mode on wireless IP LAN 38 as illustrated via dotteddouble-arrow 45. In some embodiments wherein LAN 38 is of a separatewireless transmission technology that is not compatible to cellulartransmission, then a network adapter (not shown) would be plugged intoport 13 of FIG. 1 to enable voice communication. Cell phone 9 maycommunicate on wired LAN 39 via access cable 41 connected to port 11 ofphone 9 (FIG. 1), which may be a 10-base D adapter (common in the art).When a user operating cell phone 9 logs-on to either LAN (38 or 39) heor she is assigned a temporary IP address for purposes of deviceidentification. This is illustrated via a dotted rectangle labeled IPAddress.

Once logged on to the LAN, cell phone 9 operates as any otherLAN-connected telecommunications device facilitating two-way voicecommunication. Forwarded calls to cell phone 9 will arrive via PSTN 25over trunk 37 to IP switch 35 where they are distributed accordingly. Itis important to note here that this basic embodiment illustratesconnectivity and capability only, and not routing method or controltechniques. Routing method and equipment used to control the dispositionand to send parameters of cell phone 9 when logged on to a LAN such asLANs 39 or 38 is provided in more detail below.

FIG. 3 is an overview of a routing and control system used with cellphone 9 according to an embodiment of the present invention. In thisembodiment telephony switch 31 is linked to a CTI processor 49 via a CTIconnection 51. CTI processor 49 provides intelligent routing capabilityto switch 31 by virtue of added software known as T-server software tothe inventor. A separate digital link 47 links CTI processor 49 to IPswitch 35 to provide control from within IP network 27. Other equipmentmay be assumed to be present within network 25, such as an interactivevoice response unit (IVR) and/or a statistical server.

Cell network 24 in FIG. 3 is the user's home area network, not thenetwork local to IP network 27. Calls arriving at an MSC 34 in homecellular network 24 are represented by vector 55. Routing determinationof calls 55 is based on a published cell-phone number which a callerwishing to reach cell phone 9 would dial. This is a first destinationnumber (DN 1) associated with MSC 34.

A second destination number (DN 2) is shown illustrated within IPnetwork 27 as an address (IP address) on a particular LAN such as LAN 38or 39 of FIG. 2.

Referring again to FIG. 3, when a user, via the dual-mode device 9, logsonto network 27 via LAN 38 or 39 of FIG. 2, he or she will, duringconfiguration, obtain a new and temporary IP address (DN 2) aspreviously described. Alternatively, a roaming IP address may be used,that would be fixed for the device, if the connected to network supportsthis feature. Such technologies are known to the inventor. This servicemay be made available an address allocation protocol such as DynamicHost Configuration Protocol (DHCP) which is well known in the art forthe configuration of telecommunications devices on local IP networks.

After a temporary IP address is established, a routing system comprisingconnected equipment and software as illustrated via CTI processor 49causes the input information (IP address associated with dialablecell-phone number to be made available to first destinationswitches/centers such as a switch 36 (PSTN) and MSC 34 (cell-network).Such information would be provided to MSC 34 and added to information 53if the service is provided by the cellular provider.

After configuration of cell phone 9 is complete, the IP address and DN 2are now registered at MSC 34 as illustrated via an information block 53which includes VLR and HLR information. This would be the case for acellular network hosting the service. Virtually any information may berelayed back to first destination points (DN 1) at PSTN switch 36, or atMSC 34.

If the service is provided by a non-cellular provider, then a separatedialable number must be provided in addition to the cellular phonenumber as a planned destination for incoming calls to PSTN switch 36.This service is available from most telephone-network providers in theform of the well known destination number identification service (DNIS).Alternatively, the regular number can be forwarded to the access point.

According to one embodiment of the present invention, call 55 may arriveat MSC 34 from within cellular network 24. A look-up of the HLRindicates that the owner of the device called is not within range of thelocal service area. If no current cellular service area where the useris currently operating is indicated in MSC 34 at the time of call 55,then the system looks for forwarding information and finds an IP addressassociated with the user's cell phone number. MSC 34 then routes call 55via a trunk 38 to switch 36. Call 55 is then routed on through to IPswitch 35 (via local switch 31) in network 27 via trunk 37 from switch31 based on the IP address.

An appropriate signal-conversion bridge is used to convert signal aspreviously described. Such conversion may be performed in IP switch 35or a trunk-connected bridge. The converted digital call is then routedover the LAN to DN 2, which in this case is the assigned IP address ofcell phone 9. LAN communication may be wireless or wired as previouslydescribed.

It is important to note here that the roaming distance (distance fromprimary service area to IP network as measured in consecutive cellularservice boundaries) may be considerable and that the PSTN networkcomponents illustrated in this embodiment represent both componentslocal to a primary cellular service boundary such as network 24 andthose local to a visited IP network such as network 27 as well as anylong-distance in between. First destination numbers will invariably beassigned to a local PSTN switch or service control point (SCP) whereinfurther routing is determined via information provided at the time ofconfiguration of cell phone 9 at a visited IP network.

The example described above of an instance of a cellular call 55 placedto cell phone 9 assumes that the user is taking all cellular calls in IPformat while logged-on to IP network 27. All such calls would then berouted via PSTN 25 to IP network 27. However, it may be that certaincellular calls will be exempt from IP delivery at the user's discretion.In this case, callers from known origination numbers will be routed tolocal cell network 23, local to the visited IP network, and thereforemay be received by the user of telephone 9 in normal cell-phone mode.

As an example of a COST call 57 arriving at switch 36, call 57 is heldwhile a check is made to MSC 34 which reports that the user is not inthe area and gives DN 2 information over trunk 38 to switch 34. Oncedestination is confirmed, call 57 is routed through PSTN 25 to switch31, then via trunk 37 into IP switch 35 where it may then be routed toDN 2. If cell phone 9 is not logged on to IP network 27, then call 57would be routed to the appropriate cellular service area based onregistered DN 2, which in this case, would be the actual cell-phonenumber instead of an IP address.

It will be apparent to one with skill in the art that by logging on toan IP network such as network 27, wherein CTI enhancement is made to alocally-connected PSTN switch, such as to switch 31, via CTI processor49 and control line 47, information including IP addresses, assigneddestination numbers, as well as routing preferences and rules may bemade available to primary cellular service area (23) and to PSTNswitches (36). In some embodiments, routing routines may be customizedby a user and directed to certain callers. Such options may be madeavailable through T-server control routines (known to the inventor)executing on a connected CTI processor such as processor 49.

The method and apparatus of the present invention allows a mobile userto save roaming cellular charges by routing over an IP network insteadof through a cellular service area. A corporation having many mobilereps wherein the company pays for cellular charges could realizesignificant cost savings.

It will be apparent to one with skill in the art that the presentinvention may be practiced with wide area networks (WANs) in addition toLANs without departing from the spirit and scope of the presentinvention. As long as the appropriate protocol is used and conversionmethods are observed when required, the present invention may beutilized with any IP switched packet network. Such an example would bethat of a mobile overseer of several companies or partners that areinterconnected through an IP WAN. The method and apparatus of thepresent invention should be afforded the broadest scope possible. Thespirit and scope of the present invention is limited only by the claimsthat follow.

1. A dual-mode communication device, comprising: microphone and speaker apparatus including converters for rendering audio data as audible speech, and for rendering audible speech as audio data; a first communication interface comprising circuitry for receiving and sending the audio data on a cell-phone network; and a second communication interface comprising circuitry for connecting to a local area network (LAN), and for receiving and sending the audio data on the LAN.
 2. The dual-mode communication device of claim 1 wherein the device is implemented in the form of a cell phone.
 3. The dual-mode communication device of claim 1 wherein the circuitry for connecting comprises a connector for engaging a hard-wired LAN.
 4. The dual-mode communication device of claim 1 wherein the circuitry for connecting comprises apparatus for communicating with a wireless IP-LAN.
 5. The dual-mode communication device of claim 1 further comprising control routines for negotiating a temporary IP address with the LAN upon connecting to the LAN.
 6. A system for telephone communication, comprising: an IP-LAN including an IP telephony server; a dual-mode communication device comprising first apparatus for conducting telephone calls on a cell-phone network, including a cell-phone number, and second apparatus for conducting telephone calls over the IP-LAN; a publicly-switched telephone network (PSTN) having a trunk connection to the IP telephony server; and a PSTN-connected routing server; wherein the IP telephony server, upon connection of the dual-mode communication device to the IP-LAN, assigns a temporary IP address to the connected device and informs the routing server of the connection and a destination number for the IP telephony server, and wherein the routing server then routes calls for the cell phone number to the IP telephony server, which in turn routes the calls on the IP-LAN to the temporary IP address.
 7. The system of claim 6 wherein the routing server is hosted by a cell-phone network.
 8. The system of claim 6 wherein the routing server is a part of a PSTN service control point (SCP).
 9. The system of claim 6 wherein the IP-LAN is a wireless LAN.
 10. The system of claim 6 further comprising a user-editable profile at the cell-phone routing server, enabling a user to list first origination numbers for cell network delivery and second origination numbers for LAN network delivery, wherein the cell-phone routing server delivers all calls on the cell network unless the dual-mode communication device is logged onto the LAN, in which case all calls from first origination numbers are delivered on the cell network and calls from the second origination numbers are delivered on the LAN.
 11. An IP Local Area Network (IP-LAN) system, comprising: an IP telephony server connected on the LAN and to a publicly-switched telephony trunk; and control routines executing on the IP telephony server; wherein the IP telephony server assigns a temporary IP address to a cell phone-capable device connecting on the LAN, and communicates the fact of connection and a destination number for the IP telephony server to a PSTN-connected routing server.
 12. The system of claim 11 wherein the PSTN-connected routing server is hosted by a cell-phone network.
 13. The system of claim 11 wherein the PSTN-connected routing server is a part of a PSTN service control point (SCP).
 14. The IP-LAN system of claim 11 wherein the LAN is a wireless network.
 15. The IP-LAN system of claim 11 wherein the IP telephony server associates the cell number of the cell phone-capable device with the IP address, and delivers calls received for the cell number to the cell-phone-capable device connected on the LAN.
 16. A method for minimizing cell phone charges for an organization having multiple sites, comprising steps of: (a) providing an IP-LAN at least one organization site, the LAN having a PSTN-connected IP server; (b) providing at least one dual-mode communication device for use by organization personnel, the device capable of connection and communication on both a cell-phone network and on the LAN; (c) assigning a temporary IP address to the one or more dual-mode communication devices upon connection to the LAN; (d) associating the IP address with the cell phone number of the dual-mode communication device at the IP server; (e) communicating the cell phone number and a destination number for the IP server to a PSTN-connected router; and (f) routing calls for the cell phone number to the dual-mode communication device via a cell phone network during time the dual-mode device is not logged on to the LAN, and to the IP server for routing on the LAN during time the device is logged on to the LAN.
 17. The method of claim 16 wherein in step (e) the PSTN-connected router is hosted by a cell-network provider.
 18. The method of claim 17 wherein the PSTN-connected router is a part of a PSTN service control point (SCP). 